Viscosity control is essential in many of today's manufacturing and printing processes. Viscosity is the measure of the resistance of a fluid to deformation by either shear stress or extensional stress, but is commonly perceived as the “thickness” or resistance to flow of a fluid. Viscosity can be an important quality of a finished product (e.g., a lubricant, paint, or ink) or can affect a finished product (e.g., printed material). Perhaps more importantly, an inappropriate viscosity can adversely affect modern industrial equipment. For example, if the viscosity of printing ink falls outside of an acceptable viscosity ranges, not only is print quality affected, but the printing press can also become fouled. In addition, excess fluid, especially in the case of ink, is applied is the viscosity is not correct, thus wasting natural resources required to make the ink.
Conventional falling piston viscometers measure viscosity of a fluid based on the time required for a piston to fall a distance in a bushing containing the fluid. Such conventional falling piston viscometers require that the depth of the liquid in a measuring bushing be at least 5 inches in order to get an accurate reading. This means that in many smaller applications, as the fluid is consumed or used, the level of the liquid in the tank (not shown) falls below a point where the viscometer can measure the fluid's viscosity.
Also, due to the geometric symmetry of the conventional falling piston viscometer, the piston rod must be very straight/linear in order for the viscometer to measure lower viscosities accurately. In most cases, if the rod is even slightly bent and/or has a diameter outside of a defined tolerance, the viscometer will not function properly. Thus, it can be very costly and time consuming to produce piston rods sufficiently straight due to the skill level of certain manufactures and the materials that are required.
Accordingly, there is a need for viscometers that can be incorporate less-expensive piston rods (which may or may not be sufficiently straight).
Additionally, the conventional viscosity systems are often overly-sensitive, sometimes showing minor changes that can cause unnecessary concern to a user. Thus, it would also be advantageous to produce a device that also has decreased sensitivity.